Biaxial fatigue behavior of an epoxy polymer with mean stress effect

Biaxial fatigue behavior of an epoxy polymer was investigated under cyclic shear and proportional axial-shear combined loadings with mean strains. Axial and shear strains were simultaneously measured by a non-contact real-time strain measurement system during fatigue process. Then the mechanical parameters (stress/strain components, mean stress/strain, strain energy densities, etc.) of the specimens during entire fatigue life were able to be quantitatively retrieved from the recorded stress-strain data. Multiaxial fatigue life prediction models were established upon stress-, strain- and energy-based approaches with consideration of mean stress/strain effect, where better agreement was achieved in stress-based and energy-based approaches.